An electric parking brake device of such a type has been disclosed in, for example, JP11-105680A. In the electric parking brake device, when a parking brake switch is operated, an electric actuator can perform a normal driving operation, and thus a parking lever can be driven from the returning position to the operating position (that is, the parking brake is switched to an operating state). Furthermore, when the parking brake switch is released, the electric actuator can perform a reverse driving operation, and thus the parking lever can be driven from the operating position to the returning position (that is, the parking brake is switched to a released state (a non-operating state)).
According to the description of the above-described electric parking brake device disclosed in JP11-105680A, when an electric motor provided in the electric actuator rotates in a normal direction, the electric actuator can perform the normal driving operation. Then, when electric current equal to or more than a predetermined value flows to the electric motor in a normal rotating state, the electric motor is stopped. As a result, a fixed parking-brake force can be always obtained. Furthermore, according to the description, when the electric motor provided in the electric actuator rotates in a reverse direction, the electric actuator can perform the reverse driving operation. Then, when electric current flowing to the electric motor in a reverse rotating state reaches no-load current, power of the electric motor is turned off.
The above-described electric parking brake device disclosed in JP11-105680A has an advantage (which is an advantage that it is not necessary to provide a sensor for electrically detecting a state of the parking lever) in that operating/stopping of the electric motor can be controlled using a current value flowing to the electric motor. However, a return spring which biases a brake shoe to the returning position is generally provided in the brake shoe of the drum brake. Accordingly, when the parking brake is released, the reverse driving operation of the electric actuator is assisted by the return spring.
Thus, there is a concern that a time at which electric current flowing to the electric motor in the reverse rotating state reaches the no-load current may be different from a time at which the parking lever returns to the returning position. Accordingly, there is a concern that, when the parking brake is released, inadequate return or excess return of the parking lever may occur. When inadequate return of the parking brake occurs, failure, such as brake drag, is caused. In addition, when excess return of the parking lever occurs, failure, such as response delay when performing a subsequent parking brake operation, is caused.